Section 220(b) in The Bihar Motor Vehicles Rules, 1992
(b)The mark shall be kept clean and unobscured and shall be so fixed to the trailer, that-(i)the letter on the mark is article and easily distinguishable from the rear of the trailer,(ii)the mark is either on the centre or to the right hand side or the back of the trailer, and(iii)no part thereof is at a height exceeding 122 centimeters, from ground.
